“Off with you” is a phrase used by people who lack the courtesy to say something more polite, such as “If there’s nothing else you require, I must be going,” or “I’m sorry, but I’m going to have to ask you to leave, please,” or even “Excuse me, but I believe you have mistaken my home for your own, and my valuable belongings for yours, and I must ask you to return the items in question to me, and leave my home, after untying me from this chair, as I am unable to do it myself, if it’s not too much trouble.”